The invention relates to a spark plug with centre and body electrode in which the cylindrical centre electrode comprises in its end face a blind bore in which a pin-shaped smallvolume noble metal insert is inserted and fixed by upsetting.
Such a spark plug is described in GE-PS No. 2,421,585. The fixing of the noble metal insert is effected by starting from a middle electrode whose end portion is conically widened at its outer periphery towards the end side; after insertion of the insert into the cylindrical blind bore the conically widened outer periphery of the end portion is upset onto the periphery of the cylindrical centre electrode.
It is not possible here to proceed from commercially usual centre electrodes because the latter do not have a conically widened end portion. In addition, the spark plug described has a conventional ground electrode.